Multi-Layer Golf Ball

ABSTRACT

A multi-layer golf ball that provides a consistent feel when struck with different golf clubs has a core center having a diameter D 1  and a hardness H 1 ; a first intermediate layer outward from and surrounding the core center; a second intermediate layer outward from and surrounding the first intermediate layer having a diameter D 3  and a hardness H 3 ; and a cover outward from and surrounding the second intermediate layer; wherein the ratio of H 3  to D 3  is at least about 94% of the ratio of H 1  to D 1  (H 3 /D 3 ≧0.94 H 1 /D 1 ).

This Application claims the benefit of U.S. Provisional Application62/126,249, filed Feb. 27, 2015, which is hereby incorporated byreference in its entirety.

FIELD OF THE DISCLOSURE

The invention concerns multi-layer golf balls. The inventive golf ballsare constructed to have a consistent feel when struck with differentgolf clubs.

INTRODUCTION TO THE DISCLOSURE

This section provides background information related to this disclosurebut which may or may not be prior art.

Golf balls have been constructed with multiple layers to improve playcharacteristics in the short game while maintaining good distance from atee shot. Golf balls are manufactured using a variety of processes andmaterials. The response of the ball when struck by a club may vary as afunction of the hardness of the materials chosen. For example, a harderball will typically travel further when struck by a driver than a softerball. Likewise, a softer ball will typically spin more when struck by awedge than a harder ball. Using these generalizations, many golfers willselect a ball according to their preference for distance or spincontrol.

Experienced golfers appreciate the feel of a golf ball when struck witha golf club and may select a golf ball for play based in part on whetherthe ball provides a softer or firmer feel. “Feel” is generally asubjective assessment of the response of the ball when struck by a club,though it is believed to be largely influenced by the sound of theimpact, and the acoustic response of the ball may be an important factorin ball selection to some golfers.

Specific details are given to provide a thorough understanding of thedisclosed golf ball. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the claims.

The various particular embodiments can be practiced without one or moreof the specific details or with other components, materials, and so on.In other instances, well-known structures, materials, or operations arenot shown or described in detail to avoid obscuring aspects of theembodiments. Reference throughout this specification to “oneembodiment,” “an embodiment,” or “embodiments” means that a particularfeature, structure, or characteristic is included in at least oneembodiment, and the appearances of these phrases in various placesthroughout this specification do not necessarily all refer to the sameembodiment. Furthermore, particular features, structures, orcharacteristics may be combined in other embodiments.

As used in this description, “a,” “an,” “the,” “at least one,” and “oneor more” indicate interchangeably that at least one of the item ispresent; a plurality of such items may be present unless the contextunequivocally indicates otherwise. All numerical values of parameters(e.g., of quantities or conditions) in this specification, including theappended claims, are to be understood as being modified in all instancesby the term “about” whether or not “about” actually appears before thenumerical value. “About” indicates that the stated numerical valueallows some slight imprecision (with some approach to exactness in thevalue; approximately or reasonably close to the value; nearly). If theimprecision provided by “about” is not otherwise understood in thetechnological field with this ordinary meaning, then “about” as usedherein indicates at least variations that may arise from ordinarymethods of measuring and using such parameters. In addition, disclosuresof ranges are to be understood as specifically disclosing all values andfurther divided ranges within the range. The terms “comprising,”“including,” and “having” are inclusive and therefore specify thepresence of stated features, steps, operations, elements, or components,but do not preclude the presence or addition of one or more otherfeatures, steps, operations, elements, or components. As used in thisspecification, the term “or” includes any one and all combinations ofthe associated listed items. In this description of the invention, forconvenience, “polymer” and “resin” are used interchangeably.

The weight-average molecular weight (Mw) and the number-averagemolecular weight (Mn) refer to molecular weights measured by gelpermeation chromatography (GPC) using polystyrene standards.

DRAWING

A drawing is provided and described for illustrative purposes only. Theillustrated embodiment is not intended to limit the scope of the presentdisclosure.

The FIGURE is a cross-section of an embodiment of the disclosed golfball.

DESCRIPTION

The disclosed golf ball has a core center having a diameter D1 and ahardness H1; a first intermediate layer outward from and surrounding thecore center having a diameter D2 and a hardness H2; a secondintermediate layer outward from and surrounding the first intermediatelayer and having a diameter D3 and a hardness H3; and a cover outwardfrom and surrounding the second intermediate layer having a diameter D4and a hardness H4. Each of the layers (including the core center as alayer here) has an “effective feel ratio” that is the hardness of thelayer (measured on the surface of the layer in situ on apartially-constructed ball or, in the case of the cover, afully-constructed ball) divided by the diameter of the layer (that is,of the golf ball constructed through that layer, from one point on thesurface of the layer through the golf ball center point to an oppositepoint on the surface of the layer). The effective feel ratio of thesecond intermediate layer, the ratio of H3 to D3, may be at least about94% of the effective feel ratio of the core center, the ratio of H1 toD1. The effective feel ratio of the second intermediate layer, the ratioof H3 to D3, may be greater than or equal to the effective feel ratio ofthe core center, the ratio of H1 to D1 (H3/D3>H1/D1). The effective feelratio of the second intermediate layer, the ratio of H3 to D3, may begreater than the effective feel ratio of the core center, the ratio ofH1 to D1 (H3/D3>H1/D1). For example, the effective feel ratio of thesecond intermediate layer, the ratio of H3 to D3, may be from 100% up toabout 110% or up to about 105% of the effective feel ratio of the corecenter, the ratio of H1 to D1. In another example, each of the effectivefeel ratios of the other layers (the ratio of H1 to D1, the ratio of H2to D2, and the ratio of H4 to D4) may be from about 75% to 100% of theeffective feel ratio of the second intermediate laver, the ratio of H3to D3. The thickness of the second intermediate layer may be at leastabout 0.65 mm, at least about 0.70 mm, at least about 0.75 mm, or atleast about 0.8 mm, and may be up to about 2.0 mm or up to about 1.8 mmor up to about 1.6 mm or up to about 1.5 mm or up to about 1.4 mm. Forexample, the thickness of the second intermediate layer may from about0.65 mm to about 2.0 mm or from about 0.7 mm to about 1.8 mm or fromabout 0.75 mm to about 1.6 mm or from about 0.8 mm to about 1.5 mm.

The disclosed golf ball provides a more consistent feel when struck witha range of golf clubs.

In various examples, the effective feel ratio of the core center, theratio of H1 to D1, may be from about 75% or from about 80% or from about85% or from about 90% to 100% of the effective feel ratio of the secondintermediate layer, the ratio of H3 to D3. In these or other examples,the effective feel ratio of the first intermediate layer, the ratio ofH2 to D2, may be from about 75% or from about 80% or from about 85% orfrom about 90% to 100% of the effective feel ratio of the secondintermediate layer, the ratio of H3 to D3. In these or other examples,the effective feel ratio of the cover, the ratio of H4 to D4, may befrom about 75% or from about 80% or from about 85% or from about 90% to100% of the effective feel ratio of the second intermediate layer, theratio of H3 to D3.

In general, the core center diameter may be from about 28 mm to about 36mm, the first intermediate layer thickness may be from about 2.03 mm toabout 5.28 mm, the second intermediate layer thickness may be from about0.65 mm to about 2.0 mm, and the cover thickness may be from about 0.7mm to about 1.8 mm. The D4 (the cover or golf ball diameter) may be ineach case no less than 42.67 mm to comply with the Rules of Golf forcompetitive play, or from 42.67 mm up to about 45 mm or up to about 44mm or up to about 43 mm. The second intermediate layer may have adiameter D3 of from about 39.08 mm or from about 39.25 mm or from about39.5 mm or from about 39.7 mm or from about 40 mm up to about 40.7 mm orup to about 40.8 mm or up to about 41 mm or up to about 41.15 mm or upto about 41.28 mm. For example, the second intermediate layer may have adiameter of from about 39.08 mm up to about 41.28 mm or from about 39.25mm up to about 41 mm or from about 39.5 mm up to about 40.8 mm or fromabout 39.7 mm up to about 41.15 mm or from about 40 mm up to about 40.7mm. The first intermediate layer may have a diameter D2 of from about35.08 mm or from about 35.5 mm or from about 36 mm or from about 37 mmor from about 37.9 mm up to about 38.9 mm or up to about 39.0 mm or upto about 39.3 mm or up to about 39.6 mm or up to about 39.98 mm. Forexample, the first intermediate layer may have a diameter D2 of fromabout 35.08 mm up to about 39.98 mm or from about 35.5 mm up to about39.6 mm or from about 36 mm up to about 39.3 mm or from about 37 mm upto about 39.0 mm or from about 37.9 mm up to about 38.9 mm. The corecenter may have a diameter of from about 28 mm to about 36 mm or fromabout 28 mm to about 32 mm or from about 28 mm to about 31 mm.

Examples of suitable combinations of layer dimensions are provided inTable 1, for which the units are millimeters.

TABLE 1 Core center First intermediate First intermediate Second Coverdiameter, layer thickness, layer thickness, intermediate layerthickness, Ex. D1, mm T2, mm T2, mm thickness, T3, mm T4, mm 1 28 5.295.28 0.95 1.1 2 29 4.79 4.78 0.95 1.1 3 30 4.29 4.28 0.95 1.1 4 31 3.793.78 0.95 1.1 5 32 3.29 3.28 0.95 1.1 6 33 2.79 2.78 0.95 1.1 7 34 2.292.28 0.95 1.1 8 28 5.04 5.03 1.2 1.1 9 29 4.54 4.53 1.2 1.1 10 30 4.044.03 1.2 1.1 11 31 3.54 3.53 1.2 1.1 12 32 3.04 3.03 1.2 1.1 13 33 2.542.53 1.2 1.1 14 34 2.04 2.03 1.2 1.1 15 28 4.64 4.63 2 0.7 16 29 4.144.13 2 0.7 17 30 3.64 3.63 2 0.7 18 31 3.14 3.13 2 0.7 19 32 2.64 2.63 20.7 20 33 2.14 2.13 2 0.7 21 28 5.99 5.98 0.65 0.7 22 29 5.49 5.48 0.650.7 23 30 4.99 4.98 0.65 0.7 24 31 4.49 4.48 0.65 0.7 25 32 3.99 3.980.65 0.7 26 33 3.49 3.48 0.65 0.7 27 34 2.99 2.98 0.65 0.7 28 35 2.492.48 0.65 0.7 29 28 3.54 3.53 2 1.8 30 29 3.04 3.03 2 1.8 31 30 2.542.53 2 1.8 32 31 2.04 2.03 2 1.8 33 28 4.89 4.88 0.65 1.8 34 29 4.394.38 0.65 1.8 35 30 3.89 3.88 0.65 1.8 36 31 3.39 3.38 0.65 1.8 37 322.89 2.88 0.65 1.8 38 33 2.39 2.38 0.65 1.8

The diameter of the first intermediate layer, D2, is the diameter of thecore center, D1, plus two times the thickness T2 of the firstintermediate layer: D2=D1+2×(T2); the diameter of the secondintermediate layer, D3, is the diameter of the first intermediate layer,D2, plus two times the thickness T3 of the second intermediate layer:D3=D2+2×(T3); and the diameter of the cover D4 is the diameter of thesecond intermediate layer, D3, plus two times the thickness T4 of thecover, D4=D3+2×(T4), which is the same as the diameter of the golf ball.

The hardnesses and diameters, and thus the relative feel ratios, of thecore center, first intermediate layer, second intermediate layer, andcover can be measured in different units. Hardness is measured on acurved surface of the layer. In the case of the cover, which is dimpled,hardness is measured on a land area of the curved surface of the cover.It is understood in this technical field of art that the hardnessmeasured in this way often varies from the hardness of a flat slab ofmaterial in a non-linear way that cannot be correlated, for examplebecause of effects of underlying layers. Because of the curved surface,care must be taken to center the golf ball or golf ball subassemblyunder the durometer indentor (or other applicable measuring device)before a surface hardness reading is obtained and to measure an evenarea, e.g. on the dimpled surface cover measurements are taken on a land(fret) area between dimples. For example, hardness may be measured usingthe Shore hardness C or D scale (ASTM D2240C or ASTM D2240D). Hardnessmay also be measured, for example, with an Asker durometer (ASTM D2240)or as Rockwell hardness (ASTM D785). Diameter may be measured inmillimeters, centimeters, inches, mils, and so on. Of course, thehardnesses and diameters of all of the layers are measured in the sameway and expressed in the same units in determining the relationshipsbetween the second intermediate layer and the other layers.

In particular examples, the golf ball has a core center having adiameter in millimeters D1 and a Shore D hardness H1; a firstintermediate :layer outward from and surrounding the core center havinga diameter in millimeters D2 and a Shore D hardness H2; a secondintermediate layer outward from and surrounding the first intermediatelayer and having a diameter in millimeters D3, a thickness inmillimeters D3, and a Shore D hardness H3; and a cover outward from andsurrounding the second intermediate layer having a diameter inmillimeters D4 and a Shore D hardness H4. The thickness of the secondintermediate layer, T3, is at least about 0.65 mm. Each of the layers(including the core center as a layer here) has an “effective feelratio” that is the hardness of the layer (measured on the surface of thelayer) divided by the diameter of the layer (that is, of the golf ballconstructed through that layer; from one point on the surface of thelayer through the golf ball center point to an opposite point on thesurface of the layer). The ratio of H3 to D3 may be greater than orequal to the ratio of H1 to D1 (H3/D3≧H1/D1) or may be greater than theratio of H1 to D1 (H3/D3>H1/D1), for example the ratio of H3 to D3 isequal to the ratio of H1 to D1 or is greater than the ratio of H1 to D1by no more than about 0.05 (in units of Shore D hardness/mm).

In various examples, the second intermediate layer may have an effectivefeel ratio of from about 1.5 or from about 1.6 or from about 1.65 orfrom about 1.68 up to about 1.9 or up to about 1.85 or up to about 1.8or up to about 1.75, in each case in units of Shore D hardness/mm. Amongsuitable examples of ranges for the effective feel ratio of the secondintermediate layer (H3/D3) are from about 1.5 Shore D hardness/mm) up toabout 1.9 Shore D hardness/mm, from about 1.6 Shore D hardness/mm) up toabout 1.85 Shore D hardness/mm, from about 1.65 Shore D hardness/mm) upto about 1.8 Shore D hardness/mm, and from about 1.68 Shore Dhardness/mm) up to about 1.75 Shore D hardness/mm. The effective feelratios of the remaining golf ball layers (H1/D1, H2/D2, and H4/D4) mayeach independently be in a range from equal to the effective feel ratioof the second intermediate layer, H3/D3, to about 0.42 Shore Dhardness/mm less than the effective feel ratio of the secondintermediate layer, H3/D3. For example, the effective feel ratios of theremaining golf ball layers (H1/D1, H2/D2, and H4/D4) may eachindependently be in a range from equal to the effective feel ratio ofthe second intermediate layer, H3/D3, to about 0.3 Shore D hardness/mmless than the effective feel ratio of the second intermediate layer,H3/D3 or to about 0.30 Shore D hardness/mm less than the effective feelratio of the second intermediate layer, H3/D3 or to about 0.2 Shore Dhardness/mm less than the effective feel ratio of the secondintermediate layer, H3/D3 or to about 0.15 Shore D hardness/mm less thanthe effective feel ratio of the second intermediate layer, H3/D3 or toabout 0.1 Shore D hardness/mm less than the effective feel ratio of thesecond intermediate layer, H3/D3, or to about 0.05 Shore D hardness/mmless than the effective feel ratio of the second intermediate layer,H3/D3.

In one embodiment, the second intermediate layer may have an effectivefeel ratio, H3/D3, of from about 1.65 Shore D hardness/mm to about 1.75Shore D hardness/mm, the core center may have an effective feel ratio,H1/D1, of from about 1.45 Shore D hardness/mm to about 1.75 Shore Dhardness/mm or from about 1.5 Shore D hardness/mm to about 1.7 Shore Dhardness/mm, the first intermediate layer may have an effective feelratio, H2/D2, of from about 1.35 Shore D hardness/mm to about 1.75 ShoreD hardness/mm or from about 1.4 Shore D hardness/mm to about 1.6 Shore Dhardness/mm, and the cover may have an effective feel ratio, H4/D4, offrom about 1.25 Shore D hardness/mm to about 1.6 Shore D hardness/mm orfrom about 1.3 Shore D hardness/mm to about 1.55 Shore D hardness/mm.

As shown in the FIGURE, a multi-layer golf ball 100 has a core center110 with a diameter D1 and a surface 115, a first intermediate layer 120with a diameter D2 and a surface 125 that is radially outward from andsurrounds the core center 110, a second intermediate layer 130 with adiameter D3 and a surface 135 that is radially outward from and surroundthe first intermediate layer 120, and a cover 140 with a diameter D4 anda surface 145 that forms the outermost layer of the golf ball 100. D4 isthe actual diameter of the golf ball from a land on one side through thecenter point of the golf ball to a land on the opposite side. In anembodiment in which the dimple pattern is such that there are no landareas opposite one another on the cover surface, then D4 is taken as thediameter the golf ball would have if the cover were free of dimples (thediameter of the spherical surface the golf ball would have if free ofdimples). Surface 115 has a hardness H1. Surface 125 has a hardness H2.Surface 135 has a hardness H3. Surface 145 has a hardness H4. As notedabove, H4 is measured on a land (or fret) between dimples.

The coefficient of restitution of the golf ball should be at least 0.78.The golf ball has a suitable initial velocity and distance for variousclubs when the golf ball's coefficient of restitution is at least 0.78.The golf ball coefficient of restitution is measured by firing the golfball by an air cannon at an initial velocity of 40 m/sec at a heavysteel plate about 1.2 meters away from the air cannon. The steel plateis sized to not be moved or deformed by the striking golf ball. A speedmonitoring device is located over a distance of 0.6 to 0.9 meters fromthe cannon. After striking the steel plate, the golf ball reboundsthrough the speed-monitoring device. The return velocity divided by theinitial velocity is the coefficient of restitution (COR). The COR of thecore center is measured by testing the formed core center in place ofthe golf ball. The COR of an intermediate layer is measured by testingthe a partially-constructed golf ball formed through the intermediatelayer in place of the golf ball. For example, the COR of the firstintermediate layer is tested on the first intermediate layer surroundingthe core center, while the COR of the second intermediately layer istested by forming the second intermediate layer around the firstintermediate layer and testing the resulting sphere in the COR testmethod.

The golf ball layers are each independently be made of a thermoplasticcomposition or a thermoset (i.e., crosslinked to a degree to not bethermoplastic) composition. In general, each layer will include athermoplastic or thermoset elastomer.

Nonlimiting examples of suitable thermoplastic elastomers that can beused in making the golf ball layers include metal cation ionomers ofaddition copolymers, metallocene-catalyzed block copolymers of ethyleneand α-olefins having 4 to about 8 carbon atoms, thermoplastic polyamideelastomers (PEBA or polyether block polyamides), thermoplastic polyesterelastomers, thermoplastic styrene block copolymer elastomers such aspoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene), andpoly(styrene-isoprene-styrene), thermoplastic polyurethane elastomers,thermoplastic polyurea elastomers, and dynamic vulcanizates of rubbersin these thermoplastic elastomers and in other thermoplastic matrixpolymers.

Useful metal cation ionomers of addition copolymers of ethylenicallyunsaturated acids include alpha-olefin, particularly ethylene,copolymers with C₃ to Cα,β-ethylenically unsaturated carboxylic acids,particularly acrylic or methacrylic acid. The copolymers may alsocontain one or more further comonomers, for example a softening monomersuch as an alkyl acrylate or methacrylate such as a C₁ to C₈ alkylacrylate or methacrylate ester. The α,β-ethylenically unsaturatedcarboxylic acid monomer may be from about 4 weight percent or about 6weight percent or about 8 weight percent up to about 20 weight percentor up to about 35 weight percent of the copolymer, and the softeningmonomer, when present, is preferably present in a finite amount,preferably at least about 5 weight percent or at least about 11 weightpercent, up to about 23 weight percent or up to about 25 weight percentor up to about 50 weight percent of the copolymer. The hardness of alayer may be increased by using a harder resin, for example an ionomerthat is a copolymer of and alpha-olefin and methacrylic acid, optionallywith one or more methacrylate comonomers. In general, a higher acidcontent and higher molecular weight tend to produce a harder polymer.

Nonlimiting specific examples of acid-containing ethylene copolymersinclude copolymers of ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylicacid/isobutyl acrylate, ethylene/acrylic acid/isobutyl acrylate,ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylicacid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylicacid/methyl methacrylate, and ethylene/acrylic acid/n-butylmethacrylate.

The ionomer resin may be a high acid ionomer resin. In general, ionomersprepared by neutralizing acid copolymers including at least about 16weight % of copolymerized acid residues based on the total weight of theunneutralized ethylene acid copolymer are considered “high acid”ionomers. In these high modulus ionomers, the acid monomer, particularlyacrylic or methacrylic acid, is present in about 16 to about 35 weight%. In various embodiments, the copolymerized carboxylic acid may be fromabout 16 weight %, or about 17 weight % or about 18.5 weight % or about20 weight % up to about 21.5 weight % or up to about 25 weight % or upto about 30 weight % or up to about 35 weight % of the unneutralizedcopolymer. A high acid ionomer may be combined with a “low acid” ionomerin which the copolymerized carboxylic acid is less than 16 weight % ofthe unneutralized copolymer.

The acid moiety in the ethylene-acid copolymer is neutralized by a metalcation. Suitable example cations include lithium, sodium, potassium,magnesium, calcium, barium, lead, tin, zinc, aluminum, or a combinationof these cations; in various embodiments alkali metal, alkaline earthmetal, or zinc cations are particularly useful. In various embodiments,the acid groups of the ionomer may be neutralized from about 10% or fromabout 20% or from about 30% or from about 40% to about 60% or to about70% or to about 75% or to about 80% or to about 90%.

A sufficiently high molecular weight, monomeric organic acid or salt ofsuch an organic acid may be added to the acid copolymer or ionomer sothat the acid copolymer or ionomer can be neutralized, without losingprocessability, to a level above the level that would cause the ionomeralone to become non-melt-processable. An ionomer that is highlyneutralized by including such an acid or acid salt is known in the golfball art as a highly neutralized polymer or highly neutralized acidpolymer. The high-molecular weight, monomeric organic acid its salt maybe added to the alpha-olefin-unsaturated acid copolymers before they areneutralized or after they are optionally partially neutralized to alevel between about 1 and about 100%, provided that the level ofneutralization is such that the resulting ionomer remainsmelt-processable. In generally, when the high-molecular weight,monomeric organic acid is included the acid groups of the copolymer maybe neutralized from at least about 40 to about 100%, preferably from atleast about 90% to about 100%, and most preferably 100% without losingprocessability. Such high neutralization, particularly to levels greaterthan 80%, greater than 90% or greater than 95% or most preferably 100%,without loss of processability can be achieved by (a) melt-blending theethylene α,β-ethylenically unsaturated carboxylic acid copolymer or amelt-processable salt of the copolymer with an organic acid or a salt oforganic acid, and (b) adding a sufficient amount of a cation source upto 110% of the amount needed to neutralize the total acid in thecopolymer or ionomer and organic acid or salt to the desired level toincrease the level of neutralization of all the acid moieties in themixture preferably to greater than 90%, preferably greater than 95%, orpreferably to 100%. To obtain 100% neutralization, it is preferred toadd a slight excess of up to 110% of cation source over the amountstoichiometrically required to obtain the 100% neutralization.

The high molecular weight, monomeric saturated or unsaturated acid mayhave from 8 or 12 or 18 carbon atoms to 36 carbon atoms or to less than36 carbon atoms. Nonlimiting suitable examples of the high-molecularweight, monomeric saturated or unsaturated organic acids includestearic, behenic, erucic, oleic, and linoleic acids and their salts,particularly the barium, lithium, sodium, zinc, bismuth, chromium,cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, orcalcium salts of these fatty acids. These may be used in combinations.

Grades of ionomer resins are commercially available from E.I. du Pont deNemours and Co., Inc. Wilmington, DE under the trademark Surlyn® withhardnesses from about 35-70 Shore D. Highly neutralized acid polymersare also sold by du Pont under the designation HPF with hardnesses from33 to 55 Shore D.

Thermoplastic polyolefin elastomers may also be used. These aremetallocene-catalyzed block copolymers of ethylene and α-olefins having4 to about 8 carbon atoms prepared by single-site metallocene catalysisof ethylene with a softening comonomer such as hexane-1 or octene-1, forexample in a high pressure process in the presence of a catalyst systemcomprising a cyclopentadienyl-transition metal compound and analumoxane. Octene-1 is a preferred comonomer to use. These materials arecommercially available from ExxonMobil under the tradename Exact andfrom the Dow Chemical Company under the tradename Engage™. Thermoplasticpolyolefin elastomers may be made with hardness at least from about 35Shore A to about 50 Shore D.

Suitable thermoplastic styrene block copolymer elastomers includepoly(styrene-butadiene-styrene),poly(styrene-ethylene-co-butylene-styrene),poly(styrene-isoprene-styrene), and poly(styrene-ethylene-co-propylene)copolymers. These styrenic block copolymers may be prepared by livinganionic polymers with sequential addition of styrene and the dieneforming the soft block, for example using butyl lithium as initiator.Thermoplastic styrene block copolymer elastomers are commerciallyavailable, for example, under the trademark Kraton sold by KratonPolymers U.S. LLC, Houston, Tex. with hardnesses ranging from 46 to 89Shore A (approximately 10 to 40 Shore D). Other such elastomers may bemade as block copolymers by using polymerizable non-rubber monomers inplace of the styrene, including meth(acrylate) esters such as methylmethacrylate and cyclohexyl methacrylate, and other vinyl arylenes, suchas alkyl styrenes.

Thermoplastic polyurethane elastomers such as thermoplasticpolyester-polyurethanes, polyether-polyurethanes, andpolycarbonate-polyurethanes may be used including, without limitation,polyurethanes polymerized using as polymeric diol reactants polyethersand polyesters including polycaprolactone polyesters. These polymericdiol-based polyurethanes are prepared by reaction of the polymeric diol(polyester diol, polyether diol, polycaprolactone diol,polytetrahydrofuran diol, or polycarbonate diol), one or morepolyisocyanates, and, optionally, one or more chain extension compounds.Chain extension compounds, as the term is being used, are compoundshaving two or more functional groups reactive with isocyanate groups,such as the diols, amino alcohols, and diamines. Preferably thepolymeric diol-based polyurethane is substantially linear (i.e.,substantially all of the reactants are difunctional).

Diisocyanates used in making the polyurethane elastomers may be aromaticor aliphatic. Useful diisocyanate compounds used to preparethermoplastic polyurethanes include, without limitation, isophoronediisocyanate (IPDI), methylene bis-4-cyclohexyl isocyanate (H₁₂MDI),cyclohexyl diisocyanate (CHDI), m-tetramethyl xylene diisocyanate(m-TMXDI), p-tetramethyl xylene diisocyanate (p-TMXDI), 4,4′-methylenediphenyl diisocyanate (MDI, also known as 4,4′-diphenylmethanediisocyanate), 2,4- or 2,6-toluene diisocyanate (TDI), ethylenediisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane,1,6-diisocyanatohexane (hexamethylene diisocyanate or HDI), 1,4-butylenediisocyanate, lysine diisocyanate, meta-xylylenediioscyanate andpara-xylylenediisocyanate (XDI), 4-chloro-1,3-phenylene diisocyanate,1,5-tetrahydro-naphthalene diisocyanate, 4,4′-dibenzyl diisocyanate, andcombinations of these. Nonlimiting examples of higher-functionalitypolyisocyanates that may be used in limited amounts to produce branchedthermoplastic polyurethanes (optionally along with monofunctionalalcohols or monofunctional isocyanates) include 1,2,4-benzenetriisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecanetriisocyanate, bicycloheptane triisocyanate,triphenylmethane-4,4′,4″-triisocyanate, isocyanurates of diisocyanates,biurets of diisocyanates, allophanates of diisocyanates, and the like.

Nonlimiting examples of suitable diols that may be used as extendersinclude ethylene glycol and lower oligomers of ethylene glycol includingdiethylene glycol, triethylene glycol, and tetraethylene glycol;propylene glycol and lower oligomers of propylene glycol includingdipropylene glycol, tripropylene glycol, and tetrapropylene glycol;cyclohexanedimethanol, 1,6-hexanediol, 2-ethyl-1,6-hexanediol,1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,3-propanediol,butylene glycol, neopentyl glycol, dihydroxyalkylated aromatic compoundssuch as the bis (2-hydroxyethyl) ethers of hydroquinone and resorcinol;p-xylene-α,α-diol; the bis(2-hydroxyethyl)ether of p-xylene-α,α′-diol;m-xylene-α,α′-diol, and combinations of these. Other activehydrogen-containing chain extenders that contain at least two activehydrogen groups may be used, for example, dithiols, diamines, orcompounds having a mixture of hydroxyl, thiol, and amine groups, such asalkanolamines, aminoalkyl mercaptans, and hydroxyalkyl mercaptans, amongothers. Suitable diamine extenders include, without limitation, ethylenediamine, diethylene triamine, triethylene tetraamine, and combinationsof these. Other typical chain extenders are amino alcohols such asethanolamine, propanolamine, butanolamine, and combinations of these.The molecular weights of the chain extenders preferably range from about60 to about 400. Alcohols and amines are preferred.

In addition to difunctional extenders, a small amount of a trifunctionalextender such as trimethylolpropane, 1,2,6-hexanetriol and glycerol, ormonofunctional active hydrogen compounds such as butanol ordimethylamine, may also be included.

The polyester diols used in forming a thermoplastic polyurethaneelastomer are in general prepared by the condensation polymerization ofone or more polyacid compounds and one or more polyol compounds.Preferably, the polyacid compounds and polyol compounds aredi-functional, i.e., diacid compounds and diols are used to preparesubstantially linear polyester diols, although minor amounts ofmono-functional, tri-functional, and higher functionality materials canbe included to provide a slightly branched, but uncrosslinked polyesterpolyol component. Suitable dicarboxylic acids include, withoutlimitation, glutaric acid, succinic acid, malonic acid, oxalic acid,phthalic acid, isophthalic acid, hexahydrophthalic acid, adipic acid,maleic acid, suberic acid, azelaic acid, dodecanedioic acid, theiranhydrides and polymerizable esters (e.g., methyl esters) and acidhalides (e.g., acid chlorides), and mixtures of these. Suitable polyolsinclude those already mentioned, especially the diols. Typical catalystsfor the esterification polymerization are protonic acids, Lewis acids,titanium alkoxides, and dialkyltin oxides.

A polymeric polyether or polycaprolactone diol reactant for preparingthermoplastic polyurethane elastomers may be obtained by reacting a diolinitiator, e.g., 1,3-propanediol or ethylene or propylene glycol, with alactone or alkylene oxide chain-extension reagent. Lactones that can bering opened by an active hydrogen are well-known in the art. Examples ofsuitable lactones include, without limitation, ε-caprolactone,γ-caprolactone, β-butyrolactone, β-propriolactone, γ-butyrolactone,α-methyl-γ-butyrolactone,β-methyl-γ-butyrolactone, γ-valerolactone,δ-valerolactone, γ-decanolactone, δ-decanolactone, γ-nonanoic lactone,γ-octanoic lactone, and combinations of these. In one preferredembodiment, the lactone is ε-caprolactone. Useful catalysts includethose mentioned above for polyester synthesis. Alternatively, thereaction can be initiated by forming a sodium salt of the hydroxyl groupon the molecules that will react with the lactone ring. In otherembodiments, a diol initiator may be reacted with an oxirane-containingcompound or cyclic ether to produce a polyether diol to be used in thepolyurethane elastomer polymerization. Alkylene oxide polymer segmentsinclude, without limitation, the polymerization products of ethyleneoxide, propylene oxide, 1,2-cyclohexene oxide, 1-butene oxide, 2-buteneoxide, 1-hexene oxide, tert-butylethylene oxide, phenyl glycidyl ether,1-decene oxide, isobutylene oxide, cyclopentene oxide, 1-pentene oxide,and combinations of these. The oxirane- or cyclic ether-containingcompound is preferably selected from ethylene oxide, propylene oxide,butylene oxide, tetrahydrofuran, and combinations of these. The alkyleneoxide polymerization is typically base-catalyzed. The polymerization maybe carried out, for example, by charging the hydroxyl-functionalinitiator compound and a catalytic amount of caustic, such as potassiumhydroxide, sodium methoxide, or potassium tert-butoxide, and adding thealkylene oxide at a sufficient rate to keep the monomer available forreaction. Two or more different alkylene oxide monomers may be randomlycopolymerized by coincidental addition or polymerized in blocks bysequential addition. Homopolymers or copolymers of ethylene oxide orpropylene oxide are preferred. Tetrahydrofuran may be polymerized by acationic ring-opening reaction using such counterions as SbF₆ ⁻, AsF₆ ⁻,PF₆ ⁻, SbCl₆ ⁻, BF₄ ⁻, CF₃SO₃ ⁻, FSO₃ ⁻, and ClO₄ ⁻. Initiation is byformation of a tertiary oxonium ion. The polytetrahydrofuran segment canbe prepared as a “living polymer” and terminated by reaction with thehydroxyl group of a diol such as any of those mentioned above.Polytetrahydrofuran is also known as polytetramethylene ether glycol(PTMEG).

Aliphatic polycarbonate diols that may be used in making a thermoplasticpolyurethane elastomer may be prepared by the reaction of diols withdialkyl carbonates (such as diethyl carbonate), diphenyl carbonate, ordioxolanones (such as cyclic carbonates having five- and six-memberrings) in the presence of catalysts like alkali metal, tin catalysts, ortitanium compounds. Useful diols include, without limitation, any ofthose already mentioned. Aromatic polycarbonates are usually preparedfrom reaction of bisphenols, e.g., bisphenol A, with phosgene ordiphenyl carbonate.

In various embodiments, the polymeric diol preferably has a weightaverage molecular weight of at least about 500, more preferably at leastabout 1000, and even more preferably at least about 1800 and a weightaverage molecular weight of up to about 10,000, but polymeric diolshaving weight average molecular weights of up to about 5000, especiallyup to about 4000, may also be preferred. The polymeric dioladvantageously has a weight average molecular weight in the range fromabout 500 to about 10,000, preferably from about 1000 to about 5000, andmore preferably from about 1500 to about 4000. The weight averagemolecular weights may be determined by ASTM D-4274.

The reaction of the polyisocyanate, polymeric diol, and diol or otherchain extension agent is typically carried out at an elevatedtemperature in the presence of a catalyst. Typical catalysts for thisreaction include organotin catalysts such as stannous octoate, dibutyltin dilaurate, dibutyl tin diacetate, dibutyl tin oxide, tertiaryamines, zinc salts, and manganese salts. Generally, for elastomericpolyurethanes, the ratio of polymeric diol, such as polyester diol, toextender can be varied within a relatively wide range depending largelyon the desired hardness of the final polyurethane elastomer. Forexample, the equivalent proportion of polyester diol to extender may bewithin the range of 1:0 to 1:12 and, more preferably, from 1:1 to 1:8.Preferably, the diisocyanate(s) employed are proportioned such that theoverall ratio of equivalents of isocyanate to equivalents of activehydrogen containing materials is within the range of 1:1 to 1:1.05, andmore preferably, 1:1 to 1:1.02. The polymeric diol segments typicallyare from about 35% to about 65% by weight of the polyurethane polymer,and preferably from about 35% to about 50% by weight of the polyurethanepolymer.

The selection of diisocyanate, extenders, polymeric diols, and theweight percent of the polymeric diols used takes into account thedesired specific gravity and hardness of the polyurethane elastomer.

Thermoset polyurethane layers may be made by molding, for examplereaction injection molding or compression molding processes, atwo-component mixture, one component being isocyanate-functional and thesecond component being hydroxyl-functional. At least one of thecomponents, generally the isocyanate-functional component, has afunctionality greater than two so that the product is crosslinked. Forexample, the isocyanate composition may be an oligomer, such as anisocyanurate or an isocyanate-functional product of a diisocyanate and atriol, tetraol, or higher polyol, for example trimethylolpropane. Thereaction mixture may contain a catalyst such as any of those alreadymentioned as useful for reaction isocyanate groups with hydroxyl groups.

Suitable thermoplastic polyurea elastomers may be prepared by reactionof one or more polymeric diamines or polyols with one or more of thepolyisocyanates already mentioned and one or more diamine extenders.Nonlimiting examples of suitable diamine extenders include ethylenediamine, 1,3-propylene diamine, 2-methyl-pentamethylene diamine,hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexane diamine,imino-bis(propylamine), imido-bis(propylamine),N-(3-aminopropyl)-N-methyl-1,3-propanediamine),1,4-bis(3-aminopropoxy)butane, diethyleneglycol-di(aminopropyl)ether),1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane, 1,3- or1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophoronediamine, 4,4′-diamino-dicyclohexylmethane,3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane,N,N′-dialkylamino-dicyclohexylmethane, and3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane. Polymericdiamines include polyoxyethylene diamines, polyoxypropylene diamines,poly(oxyethylene-oxypropylene) diamines, and poly(tetramethylene ether)diamines. The amine- and hydroxyl-functional extenders already mentionedmay be used as well. Generally, as before, trifunctional reactants arelimited and may be used in conjunction with monofunctional reactants toprevent crosslinking.

Thermoset polyurea layers may be made similarly to thermosetpolyurethane layers, using an amine-functional component in place or (orin combination with) the hydroxyl-functional component.

Suitable thermoplastic polyamide elastomers may be obtained by: (1)polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipicacid, sebacic acid, terephthalic acid, isophthalic acid,1,4-cyclohexanedicarboxylic acid, or any of the other dicarboxylic acidsalready mentioned with (b) a diamine, such as ethylenediamine,tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, ordecamethylenediamine, 1,4-cyclohexanediamine, m-xylylenediamine, or anyof the other diamines already mentioned; (2) a ring-openingpolymerization of a cyclic lactam, such as ε-caprolactam orw-laurolactam; (3) polycondensation of an aminocarboxylic acid, such as6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine to prepare a carboxylicacid-functional polyamide block, followed by reaction with a polymericether diol (polyoxyalkylene glycol) such as any of those alreadymentioned. Polymerization may be carried out, for example, attemperatures of from about 180° C. to about 300° C. Specific examples ofsuitable polyamide blocks include NYLON 6, NYLON 66, NYLON 610, NYLON11, NYLON 12, copolymerized NYLON, NYLON MXD6, and NYLON 46 blockcopolymer elastomers. Thermoplastic poly(ether amide) block copolymerelastomers (PEBA) are commercially available under the trademark Pebax®from Arkema.

The effects of the type and molecular weights of the soft segmentpolymeric polyols used in making polyurea elastomers and polyamideelastomers are analogous to the same effects in making thermoplasticpolyurethane elastomers.

Thermoplastic polyester elastomers have blocks of monomer units with lowchain length that form the crystalline regions and blocks of softeningsegments with monomer units having relatively higher chain lengths.Thermoplastic polyester elastomers are commercially available under thetrademark Hytrel® from E.I. du Pont de Nemours and Co., Inc. Grades witha hardness of about 25 Shore D to about 70 Shore D are available.

Suitable thermoplastic materials may include combinations ofthermoplastic elastomers. In one embodiment, the layer material includesa combination of a metal ionomer of a copolymer of ethylene and at leastone of acrylic acid and methacrylic acid, a metallocene-catalyzedcopolymer of ethylene and an α-olefin having 4 to about 8 carbon atoms,and a metal salt of an unsaturated fatty acid. This material may beprepared as described in Statz et al., U.S. Pat. No. 7,375,151 or asdescribed in Thomas J. Kennedy, III, “Process for Making ThermoplasticGolf Ball Material and Golf Ball with Thermoplastic Material, U.S.Patent Application Publication No. 2014/0274469, the entire contents ofboth being incorporated herein by reference.

Thermoplastic layer materials may include dispersed domains of curedrubbers, which may be incorporated in a thermoplastic elastomer matrixvia dynamic vulcanization of rubbers in any of these thermoplasticelastomers or in other thermoplastic polymers. Examples of suchcomposition are described John C. Chen, U.S. patent application Ser. No.14/029,136 entitled “Dynamically Crosslinked Thermoplastic MaterialProcess,” filed Sep. 17, 2013; 14/031,626 entitled “DynamicallyCrosslinked Thermoplastic Material Process,” filed Sep. 19, 2013; andSer. No. 14/029,148 entitled “Dynamically Crosslinked ThermoplasticMaterial Process,” filed Sep. 17, 2013 and in Voorheis et al, U.S. Pat.No. 7,148,279, each of which is incorporated herein by reference. Invarious embodiments, the first thermoplastic material may include athermoplastic dynamic vulcanizate of a rubber in a non-elastomericmatrix resin such as polypropylene. Thermoplastic vulcanizatescommercially available from ExxonMobil under the tradename Santoprene™are believed to be vulcanized domains of EPDM in polypropylene and areavailable in hardnesses of up to 50 Shore D.

The golf ball may have a rubber layer. As the base rubber, a variety ofrubbers (thermoplastic elastomer) may be used, such as polybutadienerubber (BR), styrene-butadiene rubber (SBR), natural rubber (NR),polyisoprene rubber OR), polyurethane rubber (PO, butyl rubber (IIR),vinyl polybutadiene rubber (VBR), ethylene-propylene rubber (EPDM),nitrile rubber (NBR), and silicone rubber. Examples of the polybutadienerubber (BR) are 1,2-polybutadiene and cis-1,4-polybutadiene. The rubberpolymers may be used singly or two or more may be used in combination.The weight-average molecular weight (Mw) may typically be at least25×10⁴, for example at least 30×10. The weight-average molecular weight(Mw) will typically be not more than 150×10⁴, for example not more than100×10⁴ for sufficient rebound while maintaining workability of thecomposition.

The cis-1,4 bond content in the diene polymer, although not subject toany particular limitation, is typically at least about 90%, or at leastabout 93%, or at least about 95%. The trans-1,4 bond content in thediene polymer, although not subject to any particular limitation, istypically not more than 7%, for example not more than about 5% or notmore than about 4%, and still more preferably not more than about 3.5%for good ball rebound. The 1,2-vinyl bond of the rubber polymers,although not subject to any particular limitation, is typically not morethan 3%, or not more than 2.0%, or not more than 1.5% for good ballrebound.

The diene polymer may be modified with a coupling agent or a polyvalentmodifier exemplified by tin, silicon, phosphorus or nitrogen-containingcompounds, epoxy group-containing compound, ester compounds andcarboxylic acids. Illustrative examples include tin tetrachloride,silicon tetrachloride, phosphorus trichloride, dibutyltin dichloride,dioctyltin bisoctylmaleate (DOTBOM), polyisocyanate compounds,polymethyl methacrylate, maleic acid, and3-glycidyloxypropyltrimethoxysilane. The coupling agents and polyvalentmodifiers react with the diene polymer to improve the cold flowproperties and may increase golf ball rebound.

The base rubber may be formulated with any of co-cross linking agentssuch as unsaturated carboxylic acids or their salts, initiatorsincluding organic peroxides, isomerization agents, peptizing agents,sulfur and organic sulfur compounds. As the co-cross linking agent, itis preferable to use, for example, an α,β-ethylenically unsaturatedcarboxylic acid, for example acrylic acid, methacrylic acid, crotonicacid, maleic acid, or fumaric acid, or a metal salt of anα,β-ethylenically unsaturated carboxylic acid, for example a zinc salt,magnesium salt or calcium salt. The co-crosslinking agent may be used inan amount, for example, based on 100 parts by weight rubber, of about 5parts or more by weight or about 10 parts by weight or more or 15 partsby weight or more and up to about 70 parts or up to about 50 parts orless by weight or not more than 40 parts by weight or not more than 35parts by weight. More co-crosslinker increases hardness, but too muchmay result in poorer durability.

Suitable examples of the organic peroxide include dicumyl peroxide,1,1-di(t-butylperoxy)-3,3,54rimethylcyclohexane, and1,1-di(t-butylperoxy)cyclohexane, organic peroxides may be used incombination, for example by using an organic peroxide having a shorterhalf-life at a given temperature with an organic peroxide having alonger half-life at the given temperature. The organic peroxide orperoxides may be included, although not subject to any particularlimitation, is typically at least about 0.05 part by weight, or at least0.1 part by weight or at least 0.15 part by weight and up to about 3parts by weight or up to about 2 parts by weight or up to about 1 partby weight or up to about 0.8 part by weight or up to about 0.6 part byweight, in each case based on 100 parts by weight of the base rubber.

Suitable examples of organosulfur compounds include thiophenols,thion.aphthols, halogenated thiophenols, and metal salts thereofillustrative examples include pentachlorothiophenol,pentafluorothiophenol, pentabromothiophenol, p-chlorothiophenol, andzinc salts thereof; diphenylpolysulfides, dihenzylpolysulfides,dibenzoylpolysulfides, dibenzothiazoylpolysulfides anddithiobenzoylpolysulfides having 2 to 4 sulfurs; alkylphenyldisulfides;and furan ring-bearing sulfur compounds and thiophene ring-bearingsulfur compounds, particularly diphenyidisulfide or the zinc salt ofpentachlorothiophenol. The organosulfur compounds may be at least about0.05 part by weight or at least about 0.2 part by weight or at leastabout 0.4 part by weight or at least about 0.7 part by weight or atleast about 0.9 part by weight and up to about 5 parts by weight or upto about 4 parts by weight or up to about 3 parts by weight or up toabout 2 parts by weight or up to about 1,5 parts by weight, based ineach case on 100 parts by weight of the base rubber polymer. The amountused is selected for good rebound at a desired layer hardness.

The vulcanization conditions are exemplified by a vulcanizationtemperature of from 100 to 200° C. and a vulcanization time of from 10to 40 minutes.

One or more plasticizers may be incorporated to adjust the hardness ofthe layer. One example of such a plasticizer is the high molecularweight, monomeric organic acid or its salt that may be incorporated, forexample, with an ionomer polymer as already described, including metalstearates such as zinc stearate, calcium stearate, barium stearate,lithium stearate and magnesium stearate. For most thermoplasticelastomers, the percentage of hard-to-soft segments is adjusted if lowerhardness is desired rather than by adding a plasticizer.

The surface hardnesses of the layers depend on the polymer selected andmay depend on degree of crosslinking (in particular for a thermosetmaterial) and on nonpolymeric materials included. Various fillers may beadded to the layer compositions for altering hardness or otherproperties of the layer. Nonlimiting examples of suitable fillersinclude clay, talc, asbestos, graphite, glass, mica, calciummetasilicate, barium sulfate, zinc sulfide, aluminum hydroxide,silicates, diatomaceous earth, carbonates (such as calcium carbonate,magnesium carbonate and the like), metals (such as titanium, tungsten,aluminum, bismuth, nickel, molybdenum, iron, copper, brass, boron,bronze, cobalt, beryllium and alloys of these), metal oxides (such aszinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide,zirconium oxide and the like), particulate synthetic plastics (such ashigh molecular weight polyethylene, polystyrene, polyethylene ionomericresins and the like), particulate carbonaceous materials (such as carbonblack, natural bitumen and the like), as well as cotton flock, celluloseflock and/or leather fiber. The amount of inorganic filler included maybe at least about 1 part by weight or at least about 5 parts by weightor at least about 10 parts by weight or at least about 15 parts byweight up to about 80 parts by weight or up to about 65 parts by weightor up to about 50 parts by weight or up to about 40 parts by weight, ineach case based on 100 parts by weight polymer in the layer composition.

Other customary additives can also be included in the layer materials,for example dispersants, antioxidants such as phenols, phosphites, andhydrazides, processing aids, surfactants, stabilizers, and so on.

Layer compositions may be made by conventional methods, such as meltmixing in a single- or twin-screw extruder, a Banbury mixer, an internalmixer, a two-roll mill, or a ribbon mixer. Typically the core center isformed first, then the first intermediate layer is molded around thecore center, the second intermediate layer is formed around the firstintermediate layer, and the cover is formed around the secondintermediate layer. The layers may be formed by injection molding orcompression molding with a typical mold temperature in the range of 150°C. to 230° C. The layers may be formed into hemispherical shells thatare then compression molded around a core center or otherpartially-constructed ball to form the next outer layer. The cover mayalso be formed on the multi-layer inner ball by injection molding,compression molding, casting, and so on. As each outer layer is added,the core center or partially constructed ball of the core center andother layer(s) may be set inside a mold, and the material of the nextouter layer may be introduced into the mold. A further layer may also bemolded on the partially-constructed ball by pre-molding a pair ofhemispherical shells from the layer material by die casting or anothermolding method, enclosing the partially-constructed ball in thehemispherical shells, and compression molding at, for example, between120° C. and 170° C. for a period of 1 to 5 minutes to attach thehemispherical shells around the inner partial ball. Thepartially-constructed ball may be surface-treated before thehemispherical shells are molded around it to increase the adhesionbetween the partially-constructed ball and hemispherical shells.Nonlimiting examples of suitable surface preparations include mechanicalor chemical abrasion, corona discharge, plasma treatment, or applicationof an adhesion promoter such as a silane or of an adhesive. The covertypically has a dimple pattern and profile to provide desirableaerodynamic characteristics to the golf ball.

The molded layers may be ground to a desired diameter after cooling.Grinding can also be used to remove flash, pin marks, and gate marks dueto the molding process.

For example, one of the core center and the first intermediate layer maybe made of one of the described rubber compositions, while the other ofthe core center and the first intermediate layer may be made of a highlyneutralized acid polymer composition, optionally further including anionomer, each as described above. The second intermediate layer mayinclude any of the thermoplastic elastomers described, for example anionomer, a polyurethane elastomer such as a polyurethane-polycarbonateelastomer, a thermoplastic polyamide elastomer, or a thermoplasticstyrene block copolymer elastomer.

The cover may be formulated with a pigment, such as a yellow or whitepigment, and in particular a white pigment such as titanium dioxide orzinc oxide. Generally titanium dioxide is used as a white pigment, forexample in amounts of from about 0.5 parts by weight or 1 part by weightto about 8 parts by weight or 10 parts by weight based on 100 parts byweight of polymer. In various embodiments, a white-colored cover may betinted with a small amount of blue pigment or brightener.

The cover may also contain one or more customary additives such asdispersants, hindered amine light stabilizers such as piperidines andoxanalides, ultraviolet light absorbers such as benzotriazoles,triazines, and hindered phenols, antioxidants such as phenols,phosphites, and hydrazides, defoaming agents, processing aids,surfactants, fluorescent materials and fluorescent brighteners,stabilizers, processing aids, and so on. Other exemplary cover materialsinclude dyes such as blue dye, pigments such as titanium dioxide andzinc oxide, and antistatic agents.

In various embodiments, the core center includes a highly neutralizedacid polymer composition, the first intermediate layer includes a rubbercomposition, the second intermediate layer includes an ionomercomposition, and the cover includes a thermoplastic or thermosetpolyurethane composition.

The golf balls can be of any size, although the USGA requires that golfballs used in competition have a diameter of at least 1.68 inches(42.672 mm) and a weight of no greater than 1.62 ounces (45.926 g). Forplay outside of USGA competition, the golf balls can have smallerdiameters and be heavier. The weight of the golf bail may be from about40 g or from about 44 g up to about 48 g, and in particularly accordingto the Rules of Golf for competitive play, preferably not more than45.93 g.

After a golf ball has been molded, it may undergo various furtherprocessing steps such as buffing, painting and marking. In aparticularly preferred embodiment of the invention, the golf ball has adimple pattern that coverage of 65% or more of the surface. The golfball typically is coated with at least one layer of a durable,abrasion--resistant and relatively non-yellowing finish coat.Optionally, a layer of coating may incorporate various color and effectpigments to give the golf ball a desired appearance. Flake effectpigments produce a gonioapparent effect in a coating layer, described inASTM F284. Suitable flake effect pigments include metallic flakepigments like aluminum flake pigments including colored aluminum flakepigment, copper flake pigments, zinc flake pigments, stainless steelflake pigments, and bronze flake pigments and pearlescent flake pigmentsincluding treated micas like titanium dioxide-coated mica pigments andiron oxide-coated mica pigments to give the coatings a differentappearance or color when viewed at different angles. Nonlimitingexamples of other suitable pigments include inorganic pigments such astitanium dioxide, carbon black, ocher, sienna, umber, hematite,limonite, red iron oxide, transparent red iron oxide, black iron oxide,brown iron oxide, ferric ammonium ferrocyanide (Prussian blue), andultramarine, and organic pigments such as metallized and non-metallizedazo reds, quinacridone reds and violets, perylene reds, copperphthalocyanine blues and greens, carbazole violet, monoarylide anddiarylide yellows, benzimidazolone yellows, tolyl orange, naphtholorange, and so on. The pigment or pigments are preferably dispersed in aresin or polymer or with a pigment dispersant, such as binder resins ofthe kind already described, according to known methods. In general, thepigment and dispersing resin, polymer, or dispersant are brought intocontact under a shear high enough to break the pigment agglomerates downto the primary pigment particles and to wet the surface of the pigmentparticles with the dispersing resin, polymer, or dispersant. Thebreaking of the agglomerates and wetting of the primary pigmentparticles are important for pigment stability and color development.Flake pigments do not agglomerate and may generally be simply stirredinto the coating.

EXAMPLES

Four golf balls were prepared as shown in Table 2. Parts are by weight(pbw). The core centers were prepared from highly neutralized acidpolymer compositions.

Examples 1 and 2 included barium sulfate to adjust the hardness of thecore center material. The hardness of each of the core centers is shownin Table 3. The Shore D hardness was measured on the formed core centerspheres. Each of the first intermediate layers of Examples 1-4 wasprepared from a cured polybutadiene rubber composition (ZDA crosslinker)containing the stated amounts of zinc oxide and barium sulfate. Thehardness of each of the first intermediate layers is shown in Table 3.The Shore D hardness was measured on the surface of the firstintermediate layer after it was formed over the core center. Each of thesecond intermediate layers of Examples 1-4 was prepared from an ionomerresin (ionomer of ethylene acid copolymer) composition. The hardness ofeach of the second intermediate layers is shown in Table 3. The Shore Dhardness was measured on the surface of the second intermediate layerafter it was formed over the of the first intermediate layer--corecenter inner sphere. Finally, a polyurethane cover containing 100 pbwpolyurethane and 10 pbw titanium dioxide was formed as the outermostgolf ball layer around the second intermediate layer. The hardness ofeach of the cover layers is shown in Table 3. Example 3 was made with asofter polyurethane. The hardness of the cover surface was measured on aland area between dimples.

TABLE 2 Example 1 Example 2 Example 3 Example 4 Core highly 100 pbw 100pbw 100 pbw 100 pbw Center neutralized acid polymer BaSO₄ 20 pbw 20 pbwDiameter 28 mm 31 mm 31 mm 31 mm Shore D 49 49 48 48 Hardness first highcis 126.3 pbw 126.3 pbw 126.3 pbw 126.3 pbw interme- polybutadiene diatecomposition layer zinc oxide 11 pbw 11 pbw 11 pbw 11 pbw barium sulfate18.5 pbw 18.5 pbw 18.5 pbw 18.5 pbw Diameter 38.6 mm 38.6 mm 38.1 mm38.6 mm Shore D 54 54 53 58 Hardness second ionomer resin 100 pbw 100pbw 100 pbw 100 pbw interme- Diameter 40.50 mm 40.50 mm 40.50 mm 40.50mm diate Shore D 68 68 70 70 layer Hardness Cover Harder TPU 100 pbw 100pbw 100 pbw Softer TPU 100 pbw TiO₂ 10 pbw 10 pbw 10 pbw 10 pbw Diameter42.67 mm 42.67 mm 42.67 mm 42.67 mm Shore D 60 60 56 63 Hardness Dimplecount 360  360  360  360 

In addition, three commercial golf balls were tested: a Titleist ProVIXgolf ball, a Callaway Tour iS golf ball, and a Nike 20XI X golf ball.The effective feel ratios for each golf ball tested are shown in Table3.

TABLE 3 Titleist Callaway Nike Example 1 Example 2 Example 3 Example 4ProVIX Tour iS 20XI X Core center Shore D hardness 49 49 48 48 49 44.550 (H1) Diameter (D1) 28 31 31 31 25 23.8 24.6 H1/D1 1.75 1.58 1.55 1.551.96 1.87 2.03 First intermediate layer Shore D hardness 54 54 53 5861.5 54.5 57 (H2) Diameter (D2) 38.6 38.1 38.6 38.6 39.42 38.5 38.6H2/D2 1.40 1.42 1.37 1.50 1.56 1.42 1.48 Second intermediate layer ShoreD hardness 68 68 70 70 63 63 68 (H3) Diameter (D3) 40.5 40.5 40.5 40.541.17 41.73 40.5 H3/D3 1.68 1.68 1.73 1.73 1.53 1.51 1.68 Cover Shore Dhardness 60 60 56 63 62 60.5 56 (H4) Diameter (D4) 42.67 42.67 42.6742.67 42.75 42.79 42.8 H4/D4 1.41 1.41 1.31 1.48 1.45 1.41 1.31 H3/D3minus −0.07 0.10 0.18 0.18 −0.43 −0.36 −0.35 H1/D1 H3/D3 minus 0.28 0.260.36 0.23 −0.03 0.09 0.20 H2/D2 H3/D3 minus 0.27 0.27 0.42 0.25 0.080.10 0.37 H4/D4 H1/D1 minus 0.31 0.17 0.24 0.07 0.41 0.46 0.72 H4/D4Largest difference 0.35 0.27 0.42 0.25 0.51 0.46 0.72 between effectivefeel ratios

Each of Example golf balls 1, 3, and 4 and the three commercial golfballs was tested for the sound produced in a sound drop test asdescribed in US Patent Application Publication No. 20014/0260635,paragraph [0091] and FIG. 13. The sound drop test was conducted byplacing a microphone array such that the stand is facing the drop trackand the frequency array at base is 14 inches from the target drop area.All microphones in frequency array must be 14 inches from the targetdrop area. A test ball is dropped in the target drop area, and the soundof its impact is recorded. The peak frequency, SPL loudness, andspectral centroid of the recorded waveform are calculated. The testresults are shown in Table 4.

TABLE 4 SPL Spectral Peak Frequency (kHz) Loudness (dBA) CentroidExample 1 3.167 −43.465 4.280 Titleist ProV1X 3.664 −43.254 3.765Callaway Tour iS 3.656 −42.991 3.699 Nike 20XI X 4.450 −42.590 4.572Example 3 3.321 −44.690 3.824 Example 4 3.304 −44.707 3.685

The results of the sound drop test show Example balls 1, 3, and 4 havelower peak frequency and lower SPL loudness values. Balls exhibitinglower peak frequency and lower SPL loudness values are generallyperceived by golfers to have excellent sound and feel when hittingshorter shot like chips or putts.

Each of Example golf balls 1, 3, and 4 and the three commercial golfballs were also tested for “feel” in this way. Three experienced golfersstruck each test ball with a putter, 9-iron, 6-iron, and driver in thatclub order. The order in which the balls were tested was random for eachplayer. Each player rated the feel of the test ball when hit with eachclub on a scale of 1 to 3, with 3 being the best feel. The average ofthe three players' ratings are recorded in Table 5.

TABLE 5 Feel (1-3, 3 is best feel) Exam- Exam- Titleist Callaway NikeExample 1 ple 3 ple 4 ProV1X Tour iS 20XI X Driver 2.3 2.7 2.7 2.0 1.71.7 6-Iron 2.7 2.7 2.7 2.7 1.3 1.0 9-Iron 2.3 2.7 2.3 2.0 1.0 1.3 Putter1.7 2.7 2.0 2.0 1.0 1.0 Average 2.3 2.7 2.4 2.2 1.3 1.3 Average 2.4 2.72.6 2.2 1.3 1.3 without putter Standard 0.4 0.0 0.3 0.3 0.3 0.3Deviation

The results in Table 5 show that the golf balls of the invention providea marked improvement in feel and in having a consistently good feel forshots with all golf clubs.

The description is merely exemplary in nature and, thus, variations thatdo not depart from the gist of the disclosure are a part of theinvention. Variations are not to be regarded as a departure from thespirit and scope of the disclosure

What is claimed is:
 1. A golf ball, comprising: a core center having adiameter in millimeters Di and a Shore D hardness Hi; a first internediate layer outward from and surrounding the core center having adiameter in millimeters D2 and a Shore D hardness H2; a secondintermediate layer outward from and surrounding the first intermediatelayer having a diameter in millimeters D3, a thickness in millimetersT3, and a Shore D hardness H3; and a cover outward from and surroundingthe second intermediate layer having a diameter in millimeters D4 and aShore D hardness H4; wherein T3 is at least about 0.65 mm; and whereinthe ratio of H3 to D3 minus the ratio of H1 to D1 (H3/D3−H1/D1) is atleast about −0.1 (Shore D hardness/mm).
 2. A golf ball according toclaim 1, wherein the ratio of H3 to D3 is greater than or equal to theratio of H1 to D1 (H3/D3≧H1/D1).
 3. A golf ball according to claim 2,wherein the ratio of H3 to D3 is equal to the ratio of H1 to D1 or isgreater than the ratio of H1 to D1 by no more than about 0.05 (Shore Dhardness/mm).
 4. A golf ball according to claim 1, wherein the maximumdifference in value between the ratios of H1 to D1 (H1/D1), H2 to D2(H2/D2), H3 to D3 (H3/D3), H4 to D4 (H4/D4) is up to about 0.42 (Shore Dhardness/mm).
 5. A golf ball according to claim 4, wherein the maximumdifference in value between the ratios of H1 to D1 (H1/D1), H2 to D2(H2/D2), H3 to D3 (H3/D3), H4 to D4 (H4/D4) is up to about 0.30 (Shore Dhardness/mm).
 6. A golf ball according to claim 1, the ratio of H3 to D3is greater than or equal to the ratio of H2 to D2 (H3/D3≧H2/D2).
 7. Agolf ball according to claim 6, wherein the ratio of H3 to D3 is equalto the ratio of H2 to D2 or is greater than the ratio of H2 to D2 by nomore than about 0.15 (Shore D hardness/mm).
 8. A golf ball according toclaim 1, wherein the ratio of H1 to D1 is greater than or equal to theratio of H4 to D4 (H1/D1≧H4/D4).
 9. A golf ball according to claim 8,wherein the ratio of H1 to D1 is equal to the ratio of H4 to D4 or isgreater than the ratio of H4 to D4 by no more than about 0.05 (Shore Dhardness/mm).
 10. A golf ball according to claim 1, wherein T3 is fromabout 0.65 mm to about 2.0 mm.
 11. A golf ball according to claim 1,wherein (a) the core center has a diameter of from about 28 mm to about36 mm or (b) the first intermediate layer has a thickness of from about2.04 mm to about 5.99 mm or both (a) and (b).
 12. A golf ball accordingto claim 1, wherein the cover has a thickness of from about 0.7 mm toabout 1.8 mm.
 13. A golf ball according to claim 1, wherein H3 is fromabout Shore D 67 to about Shore D
 72. 14. A golf ball according to claim1, wherein H1 is from about Shore D 46 to about Shore D
 50. 15. A golfbail, comprising: a core center having a diameter Di and a hardness H1;a first intermediate layer outward from and surrounding the core center;a second intermediatelayer outward from and surrounding the firstintermediate layer having a diameter D3 and a hardness H3; and a coveroutward from and surrounding the second intermediate layer; wherein theratio of H3 to D3 is at least about 94% of the ratio of H1 to D1(H3/D3≧0.94 H1/D1).
 16. A golf ball according to claim 15, wherein theratio of H3 to D3 is greater than or equal to the ratio of H1 to D1(H3/D3≧H1/D1).
 17. A golf ball according to claim 16, wherein the ratioof H3 to D3 is from 100% to about 110% of the ratio of H1 to D1.
 18. Agolf ball according to claim 16, wherein the ratio of H3 to D3 is from100% to about 105% of the ratio of H1 to D1.
 19. A golfball according toclaim 17, wherein the second intermediate layer has a thickness of atleast about 0.65 mm.
 20. A golf ball according to claim 15, wherein thefirst intermediate layer has a diameter D2 and a hardness H2, the coverhas a diameter D4 and a hardness H4: and wherein each of the ratio of H1to D1, the ratio of H2 to D2, and the ratio of H4 to D4 is from about75% to 100% of the ratio of H3 to D3.